The UK should be America's "candid friend" and offer both support and words of caution in the campaign to root out global terrorism, Liberal Democrat leader Charles Kennedy has told his party's conference.

In an emergency statement in Bournemouth Mr Kennedy implicitly agreed UK troops should be involved in "proportionate" military action but stressed the right tone was "resolve" not "war".

The way to defeat international terrorism is through international cooperation, based on international law

Charles Kennedy

The Lib Dem leader said the anger in the US was understandable but warned it could have dangerous consequences as he again argued against giving President George Bush "blank cheques" of support.

Mr Kennedy also told delegates the attacks posed "difficult dilemmas" for his party because of their implications for civil liberties.

It was the prospect of military action, however, which dominated Mr Kennedy's calls for a "proportionate response".

No crusade

"War is not the word. Nor is crusade. Resolve is," he told delegates.

"We have got to fashion a mindset, to find an approach which begins to address the roots of such evil.

"We do need to get back to those first principles. In the face of violation, be inviolate. Don't flinch. Democracy will prevail and it will."

Mr Kennedy insisted the UK had to be involved in all planning and risk assessment for any military response to the atrocities in America.

With many party delegates urging caution in an emergency debate on Monday morning, he adopted a similar tone as he spoke of the "unity of understandable anger" that had swept across America.

"The fear that can flow from that can be dangerous.

"That's where the candid friend comes in. Standing shoulder to shoulder, but always there for the occasional cautionary tap on the shoulder."

Blair has spoken with Kennedy about the attack situation

Mr Kennedy said he had spoken again to Prime Minister Tony Blair earlier on Monday.

They had agreed on their common determination to "root out terrorism wherever it may be" and the need to balance new security measures with civil freedoms.

The two party leaders also stressed that another emergency recall of Parliament should not be ruled out.

He continued: "The way to defeat international terrorism is through international cooperation, based on international law, clear intelligence and a measured and appropriate military response."

Underlining the duties of democrats, Mr Kennedy said: "We have to be especially vigilant against those people who would seek to make scapegoats of Muslims in Britain."

Freedom worries

With the government already planning a new package of security measures, Lib Dem delegates are concerned about how civil liberties will be affected.

Their leader signalled his awareness of those worries and urged realism, saying: "There will be particularly difficult dilemmas ahead for our party.

"Those difficulties will involve a gauging between the balance of the liberty of the individual against the threat that the terrorist presents to that very liberty."

'Justice not revenge'

Earlier, in the emergency debate on terrorism, foreign affairs spokesman Menzies Campbell said justice not revenge had to be the purpose of any military response.

Calling the atrocities in America a "grievous crime against humanity", Mr Campbell said it meant the creation of an international criminal court was now a clear priority.

The debate, which ended in an overwhelming vote of support for "precise and proportionate" action, was followed by a two-minute silence held in memory of those who died in America.

Winning hearts and minds

During the debate, international development spokeswoman Jenny Tonge argued that humanitarian aid for people suffering from famine and drought in Afghanistan and elsewhere could be a key weapon in preventing terrorism.

"We must bomb this area, but we must bomb it with food and aid," she said, stressing the need to create safe havens too for the millions of refugees.

"It is cheaper than military action and may win over a lot more hearts and minds."